Hair-coloring has been practiced for millennia, and continues to play an important role in modern society. A central problem in the art of hair-coloring is to provide the correct treatment—e.g. the appropriate hair-coloring composition and/or treatment parameters (e.g. treatment time, temperature, etc).
For the present disclosure, a ‘hair-coloring treatment’ is any treatment which modifies the color of hair shafts. Examples of hair-coloring treatments include hair-dying treatments (e.g. based upon artificial colorants) and bleaching. Hair-dying treatments include temporary, demi-permanent, semi-permanent or permanent hair-dying (e.g. oxidative hair-dying) treatments.
In recent years, computer-based techniques have been developed where a user provides a hair-coloring target (e.g. an LAB value), data describing the user's ‘initial hair’ (i.e. before the hair-coloring treatment) is stored in computer memory, and a customized hair-coloring composition specific for the user's hair is computed. For example, the data describing a color-state of ‘initial hair’ may be measured using an optical device such as a spectrometer or a colorimeter or a camera—this data may include an initial pre-treatment LAB value or an initial pre-treatment spectrum (e.g. reflection-spectrum) of the hair. Once this data is obtained, a number of hypothetical post-treatment hair treatments are analyzed, and a respective predicted post-treatment color state (e.g. LAB value or spectrum of the hair) is computed for each hypothetical hair-treatments.
The hypothetical hair-coloring treatments may then be scored based upon a ‘color difference’ (e.g. a distance in LAB space) between (i) the predicted post-treatment color state of the hair for each treatment and (ii) the hair-coloring target (e.g. a distance in LAB space. According to the scores, a preferred hair-coloring treatment is selected from the hypothetical or ‘candidate’ hair-coloring treatments.
In particular, the hair-coloring treatment having the minimum ‘color difference’ may be selected as the ‘best-matching’ hair-coloring treatment. The preferred hair-coloring treatment typically requires application (and hence manufacture) of one or more hair-coloring composition—each composition may be specified by quantities or concentrations of ingredients (e.g. dyes, base, coupler, lifting agent) therein.
The ingredients for manufacture of the customized hair-coloring composition may be provided by automatically dispensing the requisite ingredients from a dispenser device that is operatively linked to electronic circuitry configured to compute the hair-coloring treatment that is predicted to transform the hair from its initial color state to the target state. It is appreciated that the quality of the hair-coloring composition (i.e. its ability to indeed transform the user's physical hair to the desired color-state) is depends upon how accurately a final post-hair-coloring-treatment color state is predicted.
To date, there is an ongoing need for apparatus and methods of ascertaining a current status of a user's hair—e.g. for the purpose of accurately dispensing the correct combination of ingredients for a hair-coloring composition.